LTC1391C Просмотр технического описания (PDF) - Linear Technology
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LTC1391C Datasheet PDF : 9 Pages
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LTC1391
APPLICATIONS INFORMATION
Multiplexer Operation
Figure 1 shows the block diagram of the components
within the LTC1391 required for MUX operation. The
LTC1391 uses DIN to select the active channel and the chip
select input, CS, to switch on the selected channel as
shown in Figure 2.
When CS is high, the input data on the DIN pin is latched
into the 4-bit shift register on the rising clock edge. The
input data consists of the “EN” bit and a string of three bits
for channel selection. If “EN” bit is logic high as illustrated
in the first input data sequence, it enables the selected
channel. After the clocking in of the last channel selection
bit B0, the CS pin must be pulled low before the next rising
clock edge to ensure correct operation. Once CS is pulled
low, the previously selected channel is switched off to
ensure a break-before-make interval. After a delay of tON,
the selected channel is switched on allowing signal trans-
mission. The selected channel remains on until the next
falling edge of CS. After a delay of tOFF, the LTC1391
terminates the analog signal transmission and allows the
CLK
DIN
CONTROL
LOGIC
CS
4-BIT SHIFT
REGISTER
ANALOG INPUTS
(S0 TO S7)
MUX
BLOCK
ANALOG
OUTPUT (D)
1391 • F01
Figure 1. Simplified Block Diagram of the MUX Operation
selection of next channel. If the “EN” bit is logic low, as
illustrated in the second data sequence, it disables all
channels and there will be no analog signal transmission.
Table 1 shows the various bit combinations for channel
selection.
Table 1. Logic Table for Channel Selection
ACTIVE CHANNEL
EN
B2
B1
BO
All Off
0
X
X
X
S0
1
0
0
0
S1
1
0
0
1
S2
1
0
1
0
S3
1
0
1
1
S4
1
1
0
0
S5
1
1
0
1
S6
1
1
1
0
S7
1
1
1
1
Digital Data Transfer Operation
The block diagram of Figure 3 shows the components
within the LTC1391 required for serial data transfer. When
CS is held high, data is fed into the 4-bit shift register and
then shifted to DOUT. Data appears at DOUT after the fourth
rising edge of the clock as shown in Figure 4. The last four
CLK
DIN
CONTROL
LOGIC
CS
4-BIT SHIFT
REGISTER
DOUT
1391 F03
Figure 3. Simplified Block Diagram of the
Digital Data Transfer Operation
CLK
CS
DIN
ANY ANALOG
INPUT
D
EN B2 B1 B0
HIGH
EN LO B2 B1 B0
tON
tOFF
Figure 2. Multiplexer Operation
1391 • F02
5
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